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Trouble making Soft PLA prints

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After some months of printing normal PLA with the Ultimaker I ordered some Soft PLA from FormFutura to make some parts to dampen the amount of noise the Ultimaker produces. However, trying to print with Soft PLA has really been a hell compared with regular PLA.

The prints are based on the profile posted by Daid for soft PLA on the google groups:

 


[profile]
layer_height = 0.1
nozzle_size = 0.4
wall_thickness = 0.8
retraction_enable = True
solid_layer_thickness = 0.6
fill_density = 20
skirt_line_count = 1
skirt_gap = 2.0
print_speed = 20
print_temperature = 220
support = None
enable_raft = False
support_dual_extrusion = False
filament_diameter = 2.89
filament_density = 1.00
machine_center_x = 100
machine_center_y = 100
retraction_min_travel = 2.0
retraction_speed = 40.0
retraction_amount = 4.5
retraction_extra = 0.0
travel_speed = 150
max_z_speed = 5.0
bottom_layer_speed = 20
cool_min_layer_time = 5
fan_enabled = True
bottom_thickness = 0.3
enable_skin = False
model_scale = 0.093069064273
model_rotate_base = 0
flip_x = False
flip_y = False
flip_z = False
swap_xz = False
swap_yz = False
plugin_config = (lp1
.
raft_margin = 5
extra_base_wall_thickness = 0.0
cool_min_feedrate = 10
fan_layer = 1
fan_speed = 100
fan_speed_max = 100
raft_base_material_amount = 100
raft_interface_material_amount = 100
support_rate = 50
support_distance = 0.5
infill_type = Line
solid_top = True
fill_overlap = 30
bridge_speed = 100
sequence = Loops > Perimeter > Infill
force_first_layer_sequence = True
joris = False
retract_on_jumps_only = True
hop_on_move = False
model_rotate =
print_bed_temperature = 70
gcode_extension = gcode
object_center_x = -1
object_center_y = -1
alternative_center =
add_start_end_gcode = True
model_multiply_x = 1
model_multiply_y = 1
flipx =
flipy =
flipz =
model_matrix = 1.0,0.0,0.0,0.0,1.0,0.0,0.0,0.0,1.0
object_sink = 0.0
[alterations]
start.gcode = ;Sliced {filename} at: {day} {date} {time}
;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
;Print time: {print_time}
;Filament used: {filament_amount}m {filament_weight}g
;Filament cost: {filament_cost}
G21 ;metric values
G90 ;absolute positioning
M107 ;start with the fan off
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
G92 X0 Y0 Z0 E0 ;reset software position to front/left/z=0.0
G1 Z15.0 F{max_z_speed} ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
;go to the middle of the platform (disabled, as there is no need to go to the center)
G1 F{travel_speed}
nextobject.gcode = ;Move to next object on the platform. clear_z is the minimal z height we need to make sure we do not hit any objects.
G92 E0
G91 ;relative positioning
G1 E-1 F300 ;retract the filament a bit before lifting the nozzle, to release some of the pressure
G1 Z+0.5 E-5 F{travel_speed} ;move Z up a bit and retract filament even more
G90 ;absolute positioning
G1 Z{clear_z} F{max_z_speed}
G92 E0
G1 X{object_center_x} Y{object_center_y} F{travel_speed}
G1 F200 E6
G92 E0
end.gcode = ;End GCode
M104 S0 ;extruder heater off
M140 S0 ;heated bed heater off (if you have it)
G91 ;relative positioning
G1 E-1 F300 ;retract the filament a bit before lifting the nozzle, to release some of the pressure
G1 Z+0.5 E-5 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract filament even more
G28 X0 Y0 ;move X/Y to min endstops, so the head is out of the way
M84 ;steppers off
G90 ;absolute positioning
switchextruder.gcode = ;Switch between the current extruder and the next extruder, when printing with multiple extruders.
G92 E0
G1 E-5 F5000
G92 E0
T{extruder}
G1 E5 F5000
G92 E0
replace.csv =
support_end.gcode =
support_start.gcode =
cool_end.gcode =
cool_start.gcode =

However, most prints fail after the first couple of layers. It looks and feels at the extruder as if no more PLA is being fed into the hot end. Two evenings were spent trying to tune settings and the bed to overcome this, but this evening I first checked the extruder and found the Soft PLA 'bunched up' there, See the attached picture. I cut off the PLA and inserted a fresh end.

Extruder.jpg

The following print came out very nice for the first 2-3mm (a lot more than the first few layers I was getting before), but afterwards still failed on lack of material. See below...

Fail.jpg

 

How can I fix this problem? I am thinking it might be the dreaded plugged hot end and I am really not looking forward to opening it all up and cleaning it out, but this is probably what my weekend is going to look like anway. Any other tips?

 

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I don't think he had any retractions because of the part being printed so that's a good idea but may make no difference.

You are printing amazingly slow which should be a good thing (less head pressure). So really the only thing I can think of to mess with is the printing temperature. I would first ask the manufacturer what the recommended temp is and I would also try raising the temp to maybe 240C. I would also google to see what temp other's are using this material at. I would also set the temp to 180C manually and turn the feeder gear manual - turn about 1/3 turn and stop and watch how fast the filament comes out. repeat a few times. Maybe use a stopwatch to see how long before it slows down to almost a stop. Then try 190C 200C up to 240C.

Also it's possible the temp is too high for this speed - maybe you need to print faster or thicker (either go to 50mm/sec or .2mm layers). I know this contradicts what I just said but you have to experiment. Some materials burn (or some of the components of the pla can burn) causing a jam in the head. Usually printing faster helps this kind of thing.

 

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I end up printing at 260 without retraction when I'm printing in soft PLA and turn it into a sort of controlled ooze. Not the best technique, i know, but it works. If it's starving for PLA in some spots and hoarding in others, then I turn the speed down slightly.

 

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Quick update:

Spent most of today cleaning out the printer: opened up the hot end, pushed some PLA through it, scraped it empty with screwdriver, gave it the candle treatment, put it in a cup of acetone and cleaned it out thoroughly.

Will post pictures later/tomorrow.

Afterwards assembled the whole kit again and pushed some 'normal' pla through by had, to get a feel for the pressure in the hot end. Afterwards did the same with the soft PLA. Even though manufacturer states a print temperature of 210C, it starts feeling the same as PLA at about 240C. Will do testprint tomorrow to see if everything is fixed.

Learned/tried a few things along the way:

1. Rotate the large gear manually to get feedback on the pressure/friction when melting PLA, this really gives a lot more info that trying to extrude a few mm's more using printrun.

2. Remove the extruder spring assembly when leaving soft PLA in the machine. I've first done this today, but as I have seen a lot of creep in normal PLA, I suspect leaving it in the springforce and knurled bolt for a long time might also play a role in it not moving correctly through the extruder.

3. Playing around and just getting your hands dirty is the way to go to learn working the Ultimaker... it's not as mature and well documented as I would want it, but with the tips people give you around here and on the wiki you can get into it, and that way you get a lot more deeper understanding of the machine, making you able to troubleshoot it a lot better (which will be necessary regularly!). This should be an important part of the sales communication of Ultimaker, since if people expect to get a machine that always works perfectly they will be disappointed...

3a. what I learned: by having just the hot end (brass/alu parts) heated outside of the normal head (holding it with pliers) and then manually feeding PLA through it, you can really see the pressure required, at what kind of feedrate it starts melting back out on the rear side, etc. etc. This has really shown me the kind of problem that might take place inside the head during normal printing.

3b. Another one: by manually pushing the soft PLA through the bowden tube throug the hot-end at different temperatures you really get a feel for the amount of pressure that is built up (and how this slowly builds up). This gives me an indication how to start my next print (perhaps manually building pressure first, or adapting the gcode to slowly extrude some material before starting the print).

Will keep you up to date when printing starts, and how my settings/start code will end up.

Gr5 thanks for your great tips, I originally kinda dismissed them as I had already been fiddling with speed and temperature for the soft pla before the whole thing started going awry. However, after cleaning the head out, and manually turning the gear did I really get your tip. This is such a good way to get a feel for the pressure/resistance and the associated flow.

 

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That's because I had'nt seen it yet:-D

I have bought one in white and I love it. Difficult to achieve good results in the beginning, but I didn't use oil because I don't know what the effect will be on the material. I put a little chalk powder in the bowden tube. Blowed it out again so there will be almost nothing in it, but it worked out for me. Especially designs with a lot of retraction will benefit from greasing.

Thanks for posting the video.

 

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